Question

我正在尝试使用LINQ to EF复制以下SQL，但没有运气。

select * from Role
left join QueueAccess on Role.RoleId = QueueAccess.RoleId and queueId = 361

这是我尝试过的。

var myAccess = (from role in entity.Role.Include(p => p.QueueAccess)
join qa in entity.QueueAccess
on new { rID = role.RoleId, qID = queueId } equals new { rID = qa.RoleId, qID = qa.QueueId }
select role).ToList();

也尝试了这个。

var myAccess = entity.Role.Include(p => p.QueueAccess)
         .Where(x => x.QueueAccess.Any(a => a.QueueId == queueId)).ToList();

我继续只获取指定queueId的记录，但没有获取queueId为null的其他记录。

感谢您的帮助。

Answer 1

It's nearly always a mistake to use join in LINQ to Entities。相反，做：

var myAccess = (((ObjectQuery)from role in entity.Role
                              where role.QueueAccess.Any(a => a.QueueId == queueId)
                              select role).Include("QueueAccess")).ToList();

Answer 2

尝试这样的事情：

var access = from role in Role
             join oq in (from q in QueueAccess
                         where q.queueId = 361
                         select q) on role.RoleId equals queue.RoleId into oqs
             from queue in oqs.DefaultIfEmpty()
             select new { role.RoleId, queue.Property };

Answer 3

这样的东西也有效，将条件置于ON中，与WHERE子句相反。

join tbl3 in model.phone.Where(p => p.queue == 0  && p.phnkey == key) on x.key equals tbl3.y into a3
                            from phn in a3.DefaultIfEmpty()
                            where (phn.abc == 0 )

LINQ到EF左连接有多个条件

3 个答案: